Small Intestinal Bacterial Overgrowth Syndrome

Small intestinal bacterial overgrowth syndrome (SIBO) is a heterogeneous syndrome characterized by an increase in the number and/or presence of atypical bacteria in the small intestine. Aetiology of SIBO is usually complex, associated with disorders of protective antibacterial mechanisms such as achlorhydria, pancreatic exocrine insufficiency, immunodeficiency syndromes and anatomical abnormalities such as small intestinal obstruction, diverticula, fistulae, surgical blind loop, previous ileo-caecal resections and motility disorders. Clinical signs of SIBO may be non-specific. Most often there is dyspepsia, diarrhoea, bloating and abdominal discomfort. SIBO can sometimes lead to malebsorption, severe malenutrition and/or other syndromes associated with nutritional deficiency. The gold standard for diagnosing SIBO is still microbial investigation of jejunal aspirates. Non-invasive hydrogen breath tests are most commonly used for diagnosis of SIBO. Therapy for SIBO must be complex. It should include treatment of the underlying disease, nutritional support and cyclical gastro-intestinal selective antibiotics. Prognosis is usually serious, determined mostly by the underlying disease that led to SIBO.